1. Field of the Invention
The present invention relates to an image forming apparatus.
2. Description of Related Art
In earlier development, an image forming apparatus has been known, in which an electrostatic latent image is formed on a photoconductor drum with an LED head writing optical system where writing elements such as a plurality of light-emitting diodes (LEDs) are arranged in line and a toner image formed by adhering a toner to the electrostatic latent image is transferred to and fixed on a recording medium such as a paper so as to form an image. Some of these image forming apparatus can form images on both sides of a recording medium (have a double-sided mode), and form an image onto a backside following a front side.
When images are formed on both sides of a recoding medium as above, it is known that the recording medium shrinks at the time of forming an image on one side. This is because the recording medium to which a toner image has been transferred shrinks by heat in a fixing step. The thicker the recording medium, the more remarkable the extent of the heat shrinkage is. The deformation due to such heat shrinkage eliminates gradually after the image formation by the recording medium absorbing moisture in the air.
Therefore, in the above-described image forming apparatus, it is required to give minute deformation processing in a pixel-level according to use. Especially in a double-sided image formation, an image is formed to the backside before the deformation of the recording medium due to heat shrinkage is eliminated. Thus, it is required to perform minute deformation processing as a heat shrinkage measure. For example, it is required to form an image of the backside with a minutely reduced size than that of the front side.
As for a technique to correct such distortion of images formed on the front side and backside, JP 2005-186337A discloses setting tilts in a main scanning direction and sub scanning direction to correct a distortion of an image data based on the tilts.
However, according to this technique, an image to be formed on a recording medium is corrected only based on the tilts in main scanning direction and sub scanning direction. Thus, image formation cannot be performed flexibly, and the image aspect to be formed on each side cannot be corrected precisely in conformity with the distortion of the recording medium.